This study has as its major goal the development of methods for identifying prospective victims of sudden death. The importance of premature ventricular contractions will be studied in patients with known coronary artery disease. Twenty-four hour tape recordings obtained just prior to hospital discharge on patients recovering from myocardial infarction and repeated several months following discharge will be used to detect ventricular arrhythmias. A well established computer system will be used to scan the tapes rapidly to provide a complete analysis of all ventricular arrhythmias present. This information will be combined with information on infarct size and other clinical variables normally measured during hospitalization to define categories of patients with varying mortality rates. Finally, the computer system will be used to complete analysis on a backlog of tapes obtained on several hundred patients in which monthly recordings following hospital discharge were obtained to provide more detailed information on the natural history of ventricular arrhythmias. BIBLIOGRAPHIC REFERENCES: Ambos, H. D., Roberts, R., Oliver, G. C., Cox, Jr., J.R., and Sobel, B. E.: Infarct size: A determinant of persistence of severe ventricular dysrhythmia. Am. J. Cardiol. 37:ll6, l976. Cox, Jr., J.R., Roberts, R., Ambos, H.D., Oliver, G.C., and Sobel, B.E.: Relations between enzymatically estimated myocardial infarct size and early ventricular dysrhythmia. Circulation 53 (Suppl. I):150, l976.